通过可见光光催化剂的激素迪尔斯-阿尔德循环添加
Shishi Lin1, Michael A Ischay, Charles G Fry
1Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
Journal of the American Chemical Society
|October 29, 2011
概括
((II) 聚烯基复合物使可见光使用有效的基离子迪尔斯-阿尔德循环添加成为可能. 这种光催化法克服了电子不匹配,促进了电子丰富的二烯基分子的 [4 + 2] 循环添加.
科学领域:
- 有机金属化学 有机金属化学
- 光催化作用的光催化
- 有机合成 有机合成
背景情况:
- ((II) 聚烯基复合物是多功能光催化剂.
- 迪尔斯-阿尔德反应是有机合成的基础.
- 电子不匹配的循环添加带来了合成挑战.
研究的目的:
- 开发一个 photocatalytic 方法的激素迪尔斯-阿尔德循环添加.
- 为了利用(II) 聚烯基复合物进行高效的 [4 + 2] 循环添加.
- 为了在可见光下使电子不匹配的基板之间发生反应.
主要方法:
- 的可见光照射(II) 聚烯基复合物.
- 在循环添加反应中使用富含电子的二烯醇.
- 通过连接物修饰调节催化剂的特性.
主要成果:
- 实现了有效的基离子迪尔斯-阿尔德循环添加.
- 对于电子不匹配的基板,便于启用 [4 + 2] 循环添加.
- 连接物修改允许调整催化剂的电化学性质.
结论:
- ((II) 聚烯基复合物是激素离子迪尔斯-阿尔德反应的有效光催化剂.
- 这种方法提供了一条克服循环添加的电子限制的途径.
- 合理的催化剂设计是优化光催化性能的关键.
相关概念视频
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
Cycloaddition Reactions: MO Requirements for Thermal Activation
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
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